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Sperm cells from stem cells go on to make baby mice

A team based in the UK and Germany has succeeded in transforming stem cells into viable sperm cells, resulting in a live birth. The breakthrough could mean an end to the falling fertility rates in men.

The team, based in Newcastle, G&ouml;ttingen, Mainz and Giessen, succeeded in harvesting embryonic mouse stem cells, transforming them into viable sperm and impregnating female mice. Seven mice were born, six survived, three had abnormalities and subsequently died, but three were healthy.

The results have been published in the journal Developmental Cell. The team recognised that sperm come from 'a small population of spermatogonial stem cells (SSCs). These cells are believed to divide infinitely and to support spermatogenesis throughout life in the male,' according to the paper.

Using mice with depleted or inactive SSCs, which cause infertility, the team tried a different approach, using embryonic stem cells to achieve the same result. The resulting gametes were injected into mouse eggs using a typical human IVF technique and then inserted into the mouse womb.

The technique could in theory lead to infertile men producing their own children, rather than using donated sperm, although the law currently prevents this. The lead researcher, Professor Karim Nayernia, said in an interview with the Independent newspaper: 'The research is particularly important in helping us to understand more about the biological process by which sperm is produced. We must know this if we are to get to the root of infertility.'

The research has more applications than simple IVF - it could provide a treatment. More than half of infertility treatments are used to treat male, rather then female infertility. 'If we know more about how spermatogonial stem cells turn into sperm cells, that could be translated into treatments for men whose sperm is dysfunctional. For example, we could isolate a patient's spermatogonial cells using a simple testicular biopsy, encourage them in the laboratory into becoming functional sperm and transplant them back into the patient,' said Professor Nayernia.

The development has alarmed some groups concerned with the sanctity of the embryo. Regardless of the ethical implications, the safety and legal aspects of this research could take years to resolve, but the technique could in theory end speculation into how to reduce falling sperm rates - 30 per cent of men are now thought to be sub-fertile - with fertility problems, while a further two per cent are completely infertile. Genetic factors, smoking, obesity, too much heat, and age are all known to decrease male fertility.